Electrode adapted to be in contact with mercury



May 25, 1937. J. F. G. P. HARTMANN 2,081,376

I ELECTRODE ADAPTED TO BE IN CONTACT WITH MERCURY Filed Dec. 17. 1954 Patented May 25, 1937 ELECTRODE ADAPTED T BE IN ('ON'IACTy WITH MERCURY Julius Frederik Georg Poul Hartmann, Copenhagen, Denmark Application December 17, 1934, Serial No. 757,932 In Denmark December 23, 1933 Claims.

This invention relates to contact devices for carrying comparatively strong electric currents and comprising a mercury contact member or mass in permanent electric contact with one or more solid contact members or electrodes. The invention may for instance be applied to electrodes of electric commutators in which the movable member or members is or are produced from a mercury jet, and in which the commutation -cates a loss of electrical energy, thereby reducing the eciency of the apparatus of which the electrode is a part. Thus, in mercury jet commutators for large currents at low voltage of the kind referred to above, the intermediate vresistance between the mercury jet and the various electrodes may cause a loss amounting to about% to of the total resistance lossI of the commutator; hence it would be of the greatest importance if this material loss could be eliminated or substantially reduced, which is possible according to the present invention. Besides,l the intermediate resistance may cause constructive complications.

` An example of both drawbacks here mentioned isfound in the so-called jet-wave commutator, concerning the construction of which reference is made to my U. S. Patents Nos.' I1,306,335; 1,365,491; 1,578,287; 1,567,367 and 1,664,031. In this apparatus the intermediate resistance between the jet-wave and the electrodes being in contact therewith perceptibly inuences the. ef:A ciency of the commutator when the electrodes ashitherto are made of steel.

Due tothe intermediate current resistance, the control current,

" which in interaction with a constant magnet field face.

genioervidenskabellge Skrifter A No. 24, Copenhagen 1931, page 148, or to J ournalof Institution of Electrical Engineers vol. 68, No.' 404, August 1930.

In all electric contact devices using mercury in 5 permanent contact with one or more electrodes, the intermediate resistance would be avoided if a pure metal as copper, with which mercury amalgamates, and which is therefore "wetted by mercury, were used for the production of the electrodes. As a rule, however, such use is practically prevented by `a too quick corrosionzof the metal by the mercury.

Accordingto theinvention in a contact device for carrying heavy electric currents in which a mercury contact member isin constant `electric contact with a solid contact member or elec-A trode the latter is producedfrom a copper and aluminum alloy;

By a careful study of the problem in question it has been found that although copper is rapidly dissolved' in mercury and though aluminum is not immune to mercury, alloys of copper and aluminum do not suffer any appreciable corrosion when in contact with mercury or even wheny washed by a. continuous or intermittent flowof this metallic liquid. This is true with alloys containing from 10% down to quite a small amount-of aluminum or about 1%,V the remainder substantially copper. The surface of the alloys is in fact distinctly wetted to the same degree as a pure surface of glass is wetted by water. Dependent on the flow and on the aluminum content it retains this property for a shorter or longer time when washed by a flow of mercury.

For instance a 5% aluminum alloy will under identical conditions remain absolutely wetted for a much longer time than a 10% aluminum alloy. After many hours of washing a 10% aluo minum alloy may attain an apparently dry sur- Actually, however, the surface is not dry in so far as there still remains a close contact between mercury andthe alloy, characterized by the absence of any'appreciable intermediate r e 45 sistance. Much the same properties as pure copper-aluminum alloys with a small amount of aluminum has an alloy like Rbelbronce containing 62.98% copper30.70% zinc, 1.24% lead, 1.18% tin, 1.71% manganese and, in addition to small amounts of iron and nickel, 1.79% aluminum. It would thus seem that it is the latter element which prevents the corrosion or dissolution of the alloy.

Copper and aluminum alloys are for instance extremely well suited for electrodes of the wing type or the wedge type as employed in the jetwave commutator, which is a special form of the so-called arc-suppressing mercury jet commutator.

The said alloys also maxe it possible to construct quite new forms of electrodes for use in connection with mercury jet apparatus. This has relation to the fact that a mercury jet or jet-wave may be made to close around a body of a copper and aluminum alloy when this body is introduced into the jet or the jet wave and when it is given a suitable form and a suitable orientation relatively to the ow of mercury. Thus for instance a knife-shaped electrode with a completely wetted surface may be arranged in the plane of the jet-wave, the latter closing around the knife, and in this position used for passing the exciting current into the lwave or for tapping the commutated current out of the same.

The stated examples of the use of electrodes according to the invention are taken from the jet-wave commutator. When used insuch commutators my new contact device involves the advantages that the efllciency of the commutator is increased due to the reduction or elimination of the intermediate resistance at the electrodes, and that in several cases the construction of the commutator can be simplified'through the use of a more simple set of electrodes. The invention, however, is not limited to this apparatus; it may be used in every case where an electrical current is continuously to be conducted into mercury through a stationary electrode, and where it is important to avoid intermediate resistance. AS. range of use is referred to the whole group of electrical commutators 'and interrupters first mentioned in this specification, which besides the jet-wave commutator include numerous other commutators regarding the construction of which is referred to in my U. S. Patents Nos. 1,708,061; 1,851,704; 1,919,633 and 1,930,933, as well as to Jul. Hartmann: Mercury-Jet Commutation and Its Technical Possibilities, Engineering, Nov. 20th and Dec. 11th, 1931.

The electrodes produced according to the invention for instance can also be used in the socalled electro-magnetic pumps, see e. g. my British Patent No. 126,947, and finally, the electrochemical industry presents cases in which an electrical current is constantly to be conducted into a body of mercury through an electrode, as far as possible without intermediate resistance.

On the drawing three embodiments of contact devices according to the invention are diagrammatically shown.

Figure 1 is a diagrammatic view of a jet-wave commutator including a wedge electrode as disclosed in my U. S. Patent No. 1,664,031.

Figure 2 is a similar view of a jet-wave commutator including a curry-comb electrode as disclosed in my U. S. Patent No. 1,708,061 and Figure 3 is a perspective view of an electromagnetic pump as disclosed in my British Patent No. 126,947.

It will be understood that the construction and general mode of operation of all these apparatus is well known, and that the novel features only --reside in the particular material of which the electrodes are made as explained in the following. .-f oth in Figure l and Figure 2 the letter J designates a'jet-wave of mercury, which issues from Aa nozzle N, passes a constant magnetic field F, .is ing'constant contact -with an electrode E and coacts with several other electrodes. T is the secondary of a transformer delivering an auxiliary alternating current which in coaction with the eld F produces the waves on the jet.

In Figure 1 the jet-wave J strikes a main electrode, comprising a two-part-electrode E1, E2, between the component parts E1 and Ez of which two knives w1 and wz are placed which cut the bends of the jet-wave J at the proper moment during the commutation. The jet-wave J being during its movement towards the double electrode E1 E2 in constant contact with a wedgeshaped auxiliary electrode E arranged in the axis of the wave-figure will alternately connect this latter electrode with the electrode parts Ei and E2. The jet-wave J together with the double-electrode E1 E2 and the auxiliary electrode E thus forms a commutator which may be used for the rectification of an alternating voltage. The said auxiliary alternating current is synchronous with the latter. Although the jetwave J is cut by the wedge electrode E' it remains in constant touch therewith.- In accordance with the present invention this wedge electrode E is made of a copper-aluminum-alloy which has no appreciable intermediate resistance in contact with mercury and which as above stated is readily wetted by mercury, at least for a long time. Even after the electrode has become apparently dry there still remains a close contact between the same and the mercury jetwave J.

The jet-wave commutator illustrated in Figure 2 mainly differs from that just explained therein that the two auxiliary electrodes E and E' are formed as so-called curry-comb electrodes. The auxiliary electrode E which is in constant contact with the'jet-wave J consists of a suitable copper-aluminum alloy with not over 10% aluminum, which has no appreciable intermediate resistance in contact with mercury, while simultaneously the adhesion between a curry-combelectrode of this material and the mercury is so comparatively small that the curry-comb has no great tendency to deform the jet-wave J while continuously touching the same. Furthermore, in Figure 2 there is only used a single knife w for cutting the jet-wave.

The electro-magnetic pump shown in Figure 3 is adapted to force mercury through a pipe, for instance for the ultimate purpose of pressing a mercury jet out through a nozzle, and is based on the interaction between a magnetic field and an electric current flowing through the mercury.

The pump comprises an electromagnet f whose pole shoes g have plates m facing toward each other and covered at their inner surfaces with an insulating layer n. Into the narrow space between these insulating layers n project from above and from below respectively two spaced electrodes i. Short pieces o of insulating material are inserted into the space between the said insulating layers n both in front of and at the rear side of the electrodes, the rear insulating pieces not being shown on the drawing. Between these insulating layers and pieces and electrodes is defined a narrow horizontal slit p so that the lines of force of the magnetic field pass the slit in the direction of its shortest dimension, i. e. horizontally perpendicular upon the plates m. If this pump is built into a tube so' that the slit forms a part of its channel and if by means of the said electrodes i an electric current is conducted through mercury lling out the slit and the tube the mercury is driven through the tube owing to the interaction between the electric curaceites rent and the magnetic field since the path ot the current is mainly perpendicular to the direction .ofbihe field as well as to that of the axis of the tu In accordance'y with the 'present invention the electrodes i of the known electromagnetic pump thus described are produced from a suitable ccpper-aluminum-alloy, having no appreciable lntermediate resistance in contact with mercury whereby the eiciency of the pump can be greatly increased. Besides the electrodes are not corroded by the mercury.

For further detalls regarding the three apparatus shown on the drawing reference is made to my said earlier patents. They have been selected in the present case only as suitable examples of contact devices, in which a mercury contact member, particularly a continuously moving mercury mass, is in constant electric contact with vsolid electrodes constructed in accordance with the present invention. l

Having thus fully described my invention, I claim as new and desire to secure by Letters Patent:

1. A contact device for carrying comparatively heavy electric currents, comprising a mercury contact member and an electrode produced from a copper and aluminum alloy, said mercury contact member and electrode being in constant 30 electric contact with each other. y

2. A contact device for carrying comparatively heavy velectric currents, comprising a mercury contact member and an electrode produced from a copper and aluminum alloy, said mercury contact member and electrode being in constant electric contact with each other, said alloy containing from 1.0 to 10.0% aluminum and the retact member and electrode being in electric contact with each other, said alloy containing not over 10% aluminum and the remaindersubstantially copper. l

5. A contact device for carrying comparatively heavy electric currents, comprising amercury contact member consisting. lof a freely moving mercury jet-wave and an electrode produced from a copper and aluminum alloy, said mercury jet-wave .and electrode being in constant electric contact with each other.

JULIUB FREDERIK GEORG J POUL HARTMANN. 

